On the 124 chassis readout charts I have, there are 2 data signal readings. One is for the LED pulse system and the other is the digital.
So you can get a , let's say 4 pulse led flash, but with the scanner the same plug will give you 4 or 5 different 3 digit readings. These will pinpoint the diagnoses down to the finer point.
An example of the chart shows 2 flashes with led, but with the scanner it shows 002: ect sens- shorted
003: etc sens-open circuit
004: etc sens-implausible
005: etc sens-intermittent contact.
A "Footnote" at the bottom of the page in reference to the Led flash system states"
"Only possible uo to end of model year 1995."
I would assume , on these models that did have the built in LED, that if that feature is not there , it is no longer possible to get the Led Flash and the scanner is the tool.
Will be nice to see SB's article on this one.